Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session U2: NT.1 Novel Techniques: Spectroscopy |
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Chair: Cindy Bolme, Los Alamos National Laboratory Room: Elliott Bay |
Thursday, July 11, 2013 11:00AM - 11:15AM |
U2.00001: Coherent Raman Studies of Shocked Liquids Shawn McGrane, Kathryn Brown, Nhan Dang, Cynthia Bolme, David Moore Transient vibrational spectroscopies offer the potential to directly observe time dependent shock induced chemical reaction kinetics. We report recent experiments that couple a hybrid picosecond/femtosecond coherent anti-Stokes Raman spectroscopy (CARS) diagnostic with our tabletop ultrafast laser driven shock platform. Initial results on liquids shocked to 20 GPa suggest that sub-picosecond dephasing at high pressure and temperature may limit the application of this nonresonant background free version of CARS. Initial results using interferometric CARS to increase sensitivity and overcome these limitations will be presented. [Preview Abstract] |
Thursday, July 11, 2013 11:15AM - 11:30AM |
U2.00002: Picosecond Dynamics of Shock Compressed and Flash-Heated Nanometer Thick Films of HMX Christopher Berg, Dana Dlott New results are described for probing molecular dynamics of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) subjected to shock compression to a few GPa and/or temperature excursions exceeding thermal decomposition values (T\textgreater 500K). 5-10 nm thick films of $\delta $-HMX were grown on metallic substrates coated with monolayers of 4-nitrothiophenol. Due to shock velocities of a few nm/ps, nanometer thick films allowed picosecond time resolution of shock loading. A plastic polymer layer a few microns in thickness was spin-coated on top of HMX for shock confinement purposes. Both the monolayer and explosive layer were probed utilizing an ultrafast nonlinear coherent vibrational spectroscopy, vibrational sum-frequency generation. Shock compression pressures were estimated via comparison of the monolayer nitro transition frequency shift with static high pressure measurements in a diamond anvil cell. Temperature determinations were based on thermoreflectance measurements of the metallic substrate. [Preview Abstract] |
Thursday, July 11, 2013 11:30AM - 12:00PM |
U2.00003: \textit{In Situ} Investigation of the Dynamic Response of Energetic Materials using IMPULSE at the Advanced Photon Source Invited Speaker: Kyle Ramos The mechanical and chemical response of energetic materials is controlled by spatial heterogeneity and crystalline mechanics that evolve during impact. Traditional methods use continuum measurements to infer the microstructure response whereas advances in synchrotron capabilities and diagnostics are providing new, unique opportunities to interrogate materials in real time and \textit{in situ}. Recently the IMPULSE team has performed experiments on a gas-gun system (IMPact system for Ultrafast Synchrotron Experiments) using single X-ray bunch phase contrast imaging (PCI) and Laue diffraction at the Advanced Photon Source (APS) to examine shock-induced phenomena in energetic materials and other inert, molecular analogues. The low absorption of molecular materials maximizes x-ray beam penetration, allowing measurements in transmission using the brilliance currently available at APS Sector 32. The transmission geometry enables exciting possibilities for observing both average lattice response and spatially heterogeneous, continuum response (2 um spatial resolution, 60 ps exposure, 153ns frame-rate) in energetic materials ranging from single crystals to plastic bonded composites. This capability provides a means for linking mechanics with detonation initiation by resolving deformation mechanisms such as compaction, void collapse and jetting, cracking, dislocation-mediated plasticity and phase transformation. Representative data will be presented and discussed to illustrate current progress and future directions for this new technology. [Preview Abstract] |
Thursday, July 11, 2013 12:00PM - 12:15PM |
U2.00004: Laser-driven flyer plates for shock compression spectroscopy Dana Dlott, William Shaw, Alexander Curtis, Alexandr Banishev A laser-driven mini flyer plate system was developed for shock compression spectroscopy.\footnote{K. E. Brown, W. L. Shaw, X. Zheng, and D. D. Dlott, Rev. Sci. Instrum. \textbf{83,} 103901 (2012).} A commercial one-box 2J YAG laser produces a homogeneous top hat beam with a diffractive optic. An 8 GHz PDV characterizes flyer velocity profiles up to 5 km/s. Flyers are routinely launched with velocities reproducible to $+\backslash $-1{\%}, and the 1 mm diameter flyers have enough energy to initiate energetic materials. High-speed spectroscopic diagnostics have been synchronized. Design elements such as diameter, thickness, laser pulse duration, substrate size, and so on will be discussed. Illustrations will be presented, including monitoring shock front structures with embedded optical gauges,\footnote{K. E. Brown, Y. Fu, W. L. Shaw, and D. D. Dlott, J. Appl. Phys. \textbf{112,} 103508 (2012).} and understanding mechanisms of reactive nanomaterial impact initiation.\footnote{X. Zheng, A. D. Curtis, W. L. Shaw, and D. D. Dlott, J. Phys. Chem. C. (submitted 2012).} [Preview Abstract] |
Thursday, July 11, 2013 12:15PM - 12:30PM |
U2.00005: High resolution Broadband CARS of laser shocked materials Bruce Baer, Brian Maddox We will present preliminary data and methods detailing experiments scheduled later this year using Janus at the Jupiter Laser Facility at LLNL to obtain Coherent Anti-stokes Raman Spectra (CARS) of materials under shock conditions. High resolution ($\sim$1 cm$^{-1})$ CARS of the pre-shocked materials will demonstrate the feasibility and high precision of the methods involved. Pressures as high as 200 GPa have been previously achieved. Initially, our experiments will focus on quartz and diamond and should subsequently lead to hydrogen, deuterium and other constituents of the giant gas planets. [Preview Abstract] |
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